Portion of a fastener



FIG. 1 is a perspective front view of a portion of a fastener;

FIG. 2 is a front elevation view thereof; the rear elevation view being an identical image thereof; and,

FIG. 3 is a left side elevation view thereof; the right side view, the top plan view, and the bottom plan view being identical images thereof.

The broken lines shown in the drawings illustrate portions of the portion of a fastener that form no part of the claimed design. 

CLAIM The ornamental design for a portion of a fastener, as shown and described. 